This invention relates generally to radio-frequency (RF) circuit modules and, more particularly, to structures for reducing the effects of unwanted materials or radiation within circuit modules or packages. In a chemical or metallurgical process, a “getter” is a material added in small amounts during the process to absorb impurities. In this specification, the term “getter” is used to encompass any material or structure for reducing the effects of unwanted materials or radiation, whether by absorption, scattering, dispersion, or some other process.
In the electronics packaging industry, hydrogen is known to affect electrical performance adversely, but hydrogen is an unavoidable component in the electronics package module, such as in plated nickel layer. With the passage of time, especially in a space environment or in the low pressure environment, hydrogen can diffuse out from the materials in which it was originally contained, and cause permanent damage or adversely affect the electrical performance of the electronics module. Hydrogen getters have been developed to alleviate this problem, as described in U.S. Pat. No. 6,423,575 to Dean Tran et al., and U.S. Pat. No. 6,369,442 to Yoshio Saito. For completeness, the disclosures or these patents are incorporated by reference into this specification. A hydrogen getter structure typically includes a layer of a material known to absorb hydrogen by chemical reaction, such as titanium, and an overlying layer of a material such as palladium, which facilitates entry of hydrogen into the titanium layer but prevents oxidation of the titanium. There may also be a layer of a contact metal, such as silver or gold, underlying the titanium. One of more hydrogen getters of this type are formed of appropriate size and shape and then incorporated into the RF module, such as by affixing them to a module enclosure surface.
Other potential unwanted contaminants in RF circuit modules take the form of particles. Loose particles can arise from a number of sources during the fabrication and assembly processes and may remain in the sealed package. The need to deal with particle contamination in sealed electronics, superconducting or photonics modules has given rise to the development of particle getter structures that must also be incorporated into the module package before sealing. These may take the form of silicone materials that act in part as adhesives, to catch any loose particles that would otherwise be free to move about the sealed package. Particle getter structures in the past have been separately formed and installed in the enclosure or elsewhere in the package.
The need for absorption of radio frequency (RF) radiation in an electronics module is also well known. Especially at very high frequencies, unwanted resonances can occur within module cavities, effectively precluding or adversely affecting operation at certain frequencies. RF absorbing structures are known in the art, and have in the past also been separately formed and installed in the module package. For example, a commercially available material, ECCOSORB® RF, manufactured by Emerson & Cuming Microwave Produces, Randolph, Mass., is an RF absorber that can be machined to appropriate shapes for inclusion in an RF package housing.
Prior to the present invention, hydrogen getter structures, particle getter structures and RF absorbing structures were individually formed and installed in an electronics module package for RF application. The costs of manufacturing and assembly of the three types of getter/absorber are, therefore, a significant proportion of the total product cost of each circuit module. Moreover, each type of getter adds to the total weight of the module. For some applications, such as in spacecraft, module weight is critically important because it impacts the cost of launching the spacecraft.
Accordingly, it will be appreciated that there is still a significant need for a structure and related method that would perform the functions of a hydrogen getter, a particle getter and an RF absorber, but without imposing a requirement to form and install each type of getter/absorber separately. This would result in an RF circuit module that was less costly, more compact and lighter in weight. The present invention satisfies this need.